In raising or culturing insects such as fruit flies (Drosophila) for genetic studies and the like, the flies are placed in a culture vessel where eggs are laid and the new flies develop to the adult stage. The flies are then anesthetized in order to permit selection and separation of the flies for study and/or further culturing.
The usual practice in anesthetizing involves transferring the flies from the culture vessel to a separate anesthetizing vessel. The flies frequently escape during the transfer, presenting a nuisance in the building, and more seriously, presenting the possibility of contaminating other cultures that must be opened for transfer.
Because of these problems, methods have been proposed for anesthetizing fruit flies within a culture vessel to thereby avoid the necessity of transfer. These methods are carried out without removing the porous plug or cover of the culture vessel by passing the anesthetic as a gas through the porous plug. One proposed method requires placing the entire culture vessel in another chamber into which an anesthetic gas, such as ether, is introduced. The gas then diffuses through the porous plug and into the culture vessel. Another method, disclosed in U.S. Pat. No. 4,106,438, involves placing the mouth of the culture vessel against a nozzle which is connected to a source of anesthetic gas and causing the gas to pass through the porous plug and into the culture vessel. Still another method which has been proposed involves pouring liquid anesthetic directly onto the porous plug or closure and allowing the anesthetic to vaporize and diffuse through the plug and into the culture vessel.
All of these previously proposed methods of anesthetizing insects within a culture vessel suffer the disadvantage of being relatively slow since the anesthetic must pass through the porous plug before it comes into contact with the insects inside the culture vessel. Also, these methods are not well suited for providing accurate control over the amount of anesthetic applied. Additionally, the specialized equipment required by some of these methods, such as pressurized cylinders of anesthetic gas or special chambers, is relatively expensive and not always readily available.